Upgrading unicast nodes to multicast-capable nodes in all-optical networks

We consider the problem of upgrading unicast all-optical networks to support multicast communication. In upgrading, it is necessary to modify the existing nodes to support optical multicast switching. It is desirable to: (i) retain and use the existing node components while adding the necessary components so that the upgrading cost is small, and (ii) avoid major modification of the existing node architecture so that the upgrading overhead is small. We propose three designs to realize these two goals: (i) the pre-splitting design adds splitting modules before the existing optical switches where a splitting module can split incoming light beams into multiple ones, (ii) the post-splitting design adds splitting modules after the existing optical switches, and (iii) the pre/post-splitting design adds splitting modules before and after the existing optical switches. The pre-splitting design and post-splitting designs are simpler and involve lower upgrading overhead, while the pre/post-splitting design gives smaller blocking probability and achieves better cost-effectiveness by suitably selecting the number of splitting modules of each type.